The present invention relates to a semiconductor package that is most widely used to package semiconductor chips, and more particularly, to a semiconductor package by which an improved heat dissipation efficiency required due to an increase in the power consumption of a semiconductor chip can be obtained, the speed of a high frequency semiconductor chip can be increased, and improvement of the characteristics and stability of the qualities of semiconductor chips used in RF products can be achieved.
In general, a semiconductor package is formed by providing a semiconductor chip such as a single device, an integrated circuit device, and a hybrid circuit device, in which various electronic circuits are formed and electric wiring is made, with terminals constructed by a lead frame or the like for transmitting signals to a main board, and by subsequently molding the semiconductor chip in molding materials or the like, in order to protect the semiconductor chip from various external environments including dust, moisture, and electrical and mechanical loads and to optimize and maximize the performance of the semiconductor chip. At this time, the lead frame means a structure that serves as leads for connecting input/output pads on the semiconductor chip and electrical circuits formed in the main board, as well as a support for fixing the semiconductor package to the main board.
Packages for packaging the semiconductor chip can be classified into those of using plastic material and those of using ceramic material.
FIG. 1 illustrates an internal structure of a conventional semiconductor package using plastic material. A process of fabricating the semiconductor package shown in FIG. 1 will be described below:
(1) In a semiconductor chip attaching step, a semiconductor chip 130 is attached to a die paddle 110 of a lead frame by means of an adhesive 180;
(2) In a wiring step, bond pads 120 on the semiconductor chip 130 and inner leads 150 of the lead frame are connected by fine gold wires 170;
(3) In a molding step, the semiconductor chip 130 and the fine gold wires 170 are overmolded with an epoxy molding compound 140 in order to protect them; and
(4) In a lead forming step, outer I/O terminals 160 of a semiconductor package obtained after completion of the molding step are trimmed and formed to form out leads.
FIG. 2 illustrates an internal structure of a conventional semiconductor package using ceramic material. A process of fabricating the semiconductor package shown in FIG. 2 will be described below:
(1) In a semiconductor chip attaching step, a semiconductor chip 230 is attached to a ceramic body 290 having a cavity 292 by means of an adhesive 280;
(2) In a wiring step, bond pads 220 on the semiconductor chip 230 and inner leads 250 of the ceramic body 290 are connected by fine gold wires 270; and
(3) In a sealing step, the cavity of the ceramic body is sealed with a metallic lid 291 in order to protect the semiconductor chip 230 and the fine gold wires 270.
FIG. 3 shows a conventional semiconductor package in which the internal structure is modified in order to improve the heat dissipation efficiency of the semiconductor package using plastic material as shown in FIG. 1. A process of fabricating the semiconductor package shown in FIG. 3 will be described below:
(1) In a down-set step, a die paddle 310 of a lead frame is deeply downset;
(2) In a semiconductor chip attaching step, a semiconductor chip 330 is attached to the die paddle 310 by means of an adhesive 380;
(3) In a wiring step, bond pads 320 on the semiconductor chip 330 and inner leads 350 of the lead frame are connected by fine gold wires 370;
(4) In a molding step, the semiconductor chip 330 and the fine gold wires 370 are overmolded with an epoxy molding compound 340 in order to protect them; and
(5) In an out lead forming step, outer I/O terminals 360 of a semiconductor package obtained after completion of the molding step are trimmed and formed to form the out leads.
FIG. 4 shows another conventional semiconductor package in which the internal structure is modified in order to improve the heat dissipation efficiency of the semiconductor package using plastic material. A process of fabricating the semiconductor package shown in FIG. 4 will be described below:
(1) In a heat slug forming step, an additional heat slug 495 instead of a die paddle of a lead frame is attached to the lead frame;
(2) In a semiconductor chip attaching step, a semiconductor chip 430 is attached to the heat slug 495 in the lead frame by means of an adhesive 480;
(3) In a wiring step, bond pads 420 on the semiconductor chip 430 and inner leads 450 of the lead frame are connected by fine gold wires 470;
(4) In a molding step, the semiconductor chip 430 and the fine gold wires 470 are overmolded with an epoxy molding compound 440 in order to protect them; and
(5) In an out lead forming step, outer I/O terminals 460 of a semiconductor package obtained after completion of the molding step are trimmed and formed to form the out leads.
However, in a case where these conventional semiconductor packages are used to package a semiconductor chip having high power consumption, there is a problem in that heat generated in the semiconductor chip cannot be efficiently dissipated to the exterior thereof.
Further, in a case where the die paddle to which the semiconductor chip is attached is exposed or the heat slug attached to serve the function of the die paddle is exposed, the package is repeatedly expanded and contracted due to the heat generated from the semiconductor chip, which causes warpage of the package due to unbalance of upper and lower structures of the material constructing the package. Accordingly, there is a problem that minute delamination is formed between the exposed die paddle or heat slug and the molding material, the reliability of package is deteriorated in the long run due to infiltration of moisture and the like.
The present invention is conceived to solve the aforementioned problems in the prior art. An object of the present invention is to provide a semiconductor package with a heat-radiating canopy molded thereon and a method of fabricating the same, by which efficient heat dissipation required due to an increase in the power consumption of a semiconductor chip can be obtained, a smooth operation thereof can be made in a high frequency band to increase the speed of the semiconductor chip, and improvement of the characteristics and stability of the qualities of semiconductor chips used in RF products can be achieved.
According to the present invention, there is provided a heat dissipation type semiconductor package including a die paddle, a semiconductor chip mounted on the die paddle and a lead frame, comprising: a plurality of wires electrically connecting bond pads formed on the semiconductor chip and inner leads in the lead frame; a heat-radiating canopy attached to a top surface of the semiconductor chip; and a molding material surrounding all of the die paddle, the semiconductor chip, the inner leads and a bottom surface of the heat-radiating canopy; wherein the top surface of the heat-radiating canopy is is exposed to the exterior, and a portion of the bottom surface of the heat-radiating canopy being in contact with the semiconductor chip is recessed.
According to the present invention, there is also provided a heat dissipation type semiconductor package including a substrate, a die paddle formed on the substrate, a semiconductor chip mounted on the die paddle, and inner leads attached to the substrate and serving as electrical contacts, comprising: a plurality of wires electrically connecting bond pads formed on the semiconductor chip and the inner leads; a heat-radiating canopy attached to a top surface of the semiconductor chip; a molding material surrounding all of the die paddle, the semiconductor chip, the inner lead and a bottom surface of the heat-radiating canopy; and solder balls mounted on a bottom surface of the substrate and serving as electrical inputs/outputs; wherein the top surface of the heat-radiating canopy is exposed to the exterior, and a portion of the surface of the heat-radiating canopy being in contact with the semiconductor chip is recessed.
According to the present invention, there is also provided a method of fabricating a heat dissipation type semiconductor package, comprising the steps of: attaching a semiconductor chip to a die paddle of a lead frame of a semiconductor package; connecting bond pads on the semiconductor chip and inner leads in the lead frame by means of wires; attaching a heat-radiating canopy to a top surface of the semiconductor chip; performing a molding in such a manner that a top surface of the heat-radiating canopy is exposed to the exterior; and trimming and forming out leads in the semiconductor package obtained after completion of the molding so as to form I/O terminals of the semiconductor package.
According to the present invention, there is also provided a method of fabricating a heat dissipation type semiconductor package, comprising the steps of: forming a die paddle and inner leads on a substrate; attaching a semiconductor chip to the die paddle; connecting bond pads on the semiconductor chip and the inner leads by means of wires; attaching a heat-radiating canopy to a top surface of the semiconductor chip by means of an adhesive; performing a molding in such a manner that a top surface of the heat-radiating canopy is exposed to the exterior; and forming solder balls on a bottom surface of the semiconductor package after completion of the molding step.
More preferably, the semiconductor chip attaching step comprises a step of attaching the semiconductor chip by means of an adhesive and then curing the adhesive using an electric oven or a heater block.
More preferably, the wires are made of any one of gold, copper, aluminum, and an arbitrary combination thereof.
More preferably, a central portion of the heat-radiating canopy is recessed so that a portion of the beat-radiating canopy, which is located above the top surface of the semiconductor chip, is in contact with the semiconductor chip and the remaining portions of the heat-radiating canopy are not in contact with the semiconductor chip.
More preferably, when the heat-radiating canopy is attached to the top surface of the semiconductor chip, the heat-radiating canopy is caused to be in contact with an active area of the semiconductor chip.
More preferably, the heat-radiating canopy is made of a material selected from a group consisting of thermal conductive materials, electrically conductive materials and an arbitrary combination thereof.
More preferably, the heat-radiating canopy has a round shape or a polygonal shape depending on the shape of the semiconductor package.
More preferably, an edge of the heat-radiating canopy is curved toward a bottom surface of the semiconductor package.
More preferably, an edge of the heat-radiating canopy is formed with a portion protruding toward a bottom surface of the semiconductor package.
More preferably, the heat-radiating canopy attaching step comprises a step of attaching the heat-radiating canopy to the top surface of the semiconductor chip by means of an adhesive and then curing the adhesive using an electric oven or a heater block.
More preferably, the adhesive is selected from a group consisting of thermo-plastic adhesive epoxy, thermo-set adhesive epoxy, thermal conductive epoxy, electrically conductive epoxy, an adhesive tape, and an arbitrary combination thereof.
More preferably, a plurality of projections are formed on the exposed surface of the heat-radiating canopy.
More preferably, an external heat slug is attached to the exposed surface of the heat-radiating canopy.
More preferably, a post-mold curing process is performed by using an electric oven, after the molding step.
More preferably, the exposed surface of the heat-radiating canopy is polished or defleshed.
More preferably, the out leads or the exposed surface of the heat-radiating canopy are plated.